SATA_ID_ATA_INFO_LEN
page_buf[2] = (SATA_ID_ATA_INFO_LEN >> 8) & 0xff;
page_buf[3] = SATA_ID_ATA_INFO_LEN & 0xff;
count = MIN(bp->b_bcount, SATA_ID_ATA_INFO_LEN + 4);